Powers' career was blighted by several drug busts. After arrest for possession of marijuana, while awaiting trial he was searched again by police who found more marijuana, then amphetamines in his apartment. He received a one-to-ten-year sentence at Folsom State Prison. To raise money for his defense, he sold the publishing rights for "Get Together" to the manager of the Kingston Trio (the Trio had recorded the song in 1964).

In the late 1960s, he signed as a solo artist with CBS's Epic Records, releasing the solo LP Dino Valente. He traveled with Quicksilver's Gary Duncan to New York in January 1969 to form a new band to be called "The Outlaws", while Quicksilver's noted album Happy Trails album appeared in March. While Valenti and Duncan were in New York, British keyboardist Nicky Hopkins joined Quicksilver for their third album, Shady Grove (December 1969).

The Outlaws came to naught and the two musicians joined Quicksilver at a New Year's Eve concert by the band. Eight of the nine songs on the group's next album, Just for Love (August, 1970) were written by Valenti/Powers, six of them under the pseudonym of "Jesse Otis Farrow". He remained the primary songwriter on their next album, in December, What About Me?. Despite occasional personnel changes the band released Quicksilver (1971) and Comin' Thru (1972) before calling it quits. The 2-LP Anthology was issued in 1973 and a tour and album, Solid Silver, appeared in 1975.

Powers underwent brain surgery for an arteriovenous malformation (AVM) in the late 1980s. In spite of suffering from short-term memory loss and the effects of anti-convulsive medications, he continued to write songs and play with fellow Marin County musicians.

His last major performance was a benefit at San Francisco's Great American Music Hall. He died suddenly at his home in Santa Rosa, California on November 16, 1994, leaving behind a younger sister, Katherine (Kay), and two sons, Joli and Sterling.